Control methods for popping popcorn

ABSTRACT

Apparatus and methods for popping popcorn comprise a heated kettle which is controlled and monitored according to the temperature of the kettle. The kettle is initially heated to a start cook temperature and a buzzer and light alert an operator to add uncooked popcorn and oil to the kettle which lowers the temperature of the kettle below a predetermined start temperature and initiates a cooking cycle. An oil pump system is enabled at the initiation of the cooking cycle for adding oil to the kettle. As the popcorn and oil cook, the kettle temperature increases and passes through a predetermined dump temperature and the kettle automatically tilts and dumps the cooked popcorn. After the dump, the kettle temperature increases to the start cook temperature again and the buzzer and light are activated to alert the operator to add another batch of ingredients for consecutive batches of popcorn.

RELATED APPLICATIONS AND PRIORITY

This application is a continuation in part application of U.S. patentapplication Ser. No. 09/212,667, filed Dec. 16, 1998, entitled“Apparatus for Popping Popcorn,” now U.S. Pat. No. 6,000,318, whichapplication in turn is a divisional application of Ser. No. 08/910,756,filed Aug. 13, 1997, and entitled “Method for Popping Popcorn,” now U.S.Pat. No. 5,871,792, which application in turn is a divisionalapplication of application Ser. No. 08/633,580, filed Apr. 17, 1996, andentitled “Automatic Popcorn Popper with Thermal Controller,” now U.S.Pat. No. 5,743,172, which application, in turn, is acontinuation-in-part application of application Ser. No. 08/345,303,filed Nov. 28, 1994, and entitled “Automated Corn Popper,” now U.S. Pat.No. 5,694,830, which applications and issued patents are incorporatedherein by reference in their entirety.

FIELD OF THE INVENTION

This invention relates generally to popcorn poppers and morespecifically to a automatic or manual popcorn poppers which producepopcorn in consecutive batches while reducing the amount of attentionrequired from an operator and while producing a consistently highquality of popped corn. This invention also relates to an improvedmethod for popping popcorn.

BACKGROUND OF THE INVENTION

Popcorn is mass-produced for sale at movies and other events incommercial popcorn poppers which include an enclosed, transparentcabinet containing a tiltable kettle suspended above a catch area orplatform. The kettle is heated and uncooked popcorn kernels are placedtherein to be cooked and popped. Once the kernels are popped, the kettleis manually tilted and the popcorn spills onto the platform to bescooped up, packaged and sold to customers.

Conventionally, commercial popcorn poppers have been manually operatedand have required an operator's constant attention for cooking thekernels and subsequently dumping the popped popcorn. For example, anoperator would load the kettle with popping oil and unpopped cornkernels and then listen and watch for the unpopped corn to pop. When theoperator decided, somewhat arbitrarily, that the corn was sufficientlypopped, they would then dump the kettle and spill the popcorn onto theserving platform. Additional oil and corn would then be added for thenext batch. While such conventional popcorn poppers are generallyeffective in mass-producing popcorn; the constant attention they requireprevents the operator from other important tasks, such as selling thepopcorn and other concession products, taking money and generallyservicing customers.

As may be appreciated, the multiple duties entrusted concessionaireoperators are not conducive to having them constantly monitor a popcornpopper. If attention is diverted for an extended length of time, thepopcorn is susceptible to being burned or overcooked. In addition to thewaste of burned popcorn, the aroma of the burned popcorn is notattractive to customers and may actually discourage purchases.Furthermore, if the operator inadvertently dumps the burned corn ontothe platform, it will contaminate the usable popcorn which has alreadybeen produced and may render the entire batch inedible and thusunusable. Still further, the results and mess from burned popcorn is noteasy to clean. The kettle is hot and must be allowed to cool before theburned popcorn is removed and the kettle placed back in service.

Additionally, the arbitrary nature of the dumping process withconventional poppers makes them subject to messes associated withpremature dumping. For example, if the operator mistakenly believes thatthe corn has been completely popped and the oil used when indeeduncooked corn and oil remains in the kettle, tilting the kettle willspill oil onto the serving platform and possibly onto the counter. Suchspills ruin and waste popcorn and create a mess which must be cleaned,adding to the already numerous tasks of a concessionaire.

Still further, too much oil may be added for a particular cooking cycle,and even if the cooking cycle is completed, excess oil might be left,again resulting in a mess upon dumping of the batch. For example, oneoperator may load the uncooked corn and oil for a batch, and anotheroperator may subsequently and inadvertently load more oil, believing ithad not been added. The excess oil does not burn off or cook and remainsin the kettle. Not only is a mess created upon dumping, but the excessoil may also foul the batch of popcorn.

Another drawback of conventional popcorn poppers is the inherent delayswhich will occur between cooked batches of popcorn. When the popcorn hasbeen cooked and dumped, the operator may begin serving it to customerswithout replenishing the supply of corn and oil and starting the nextbatch. Therefore, the next batch of popcorn will not be produced untilthe operator consciously sets aside time from his other activities to doso. Such delays interrupt production rates and introduce inefficienciesinto the operation which reduce popcorn sales.

It is also desirable to pop popcorn consistently so that it produceshigh quality consistent taste from batch to batch. The vagaries of priorsystems leave much to chance in this regard so that batches of corn areundercooked, burned or the like and at the least are inconsistent intaste.

Still another but related drawback to conventional popping processes ormechanisms is that they sometimes provide inconsistent or improperheating of the popcorn so that proper expansion of the kernels uponpopping is not achieved. Particularly, when the heat is too high, thesteam from the kernel is prematurely forced out and the popped kernel issmall. If the temperature is too low, the kernels do not experienceproper hull expansion and brittleness at popping and the popped kernelsare small. It will also be appreciated that small popcorn kernels reducethe yield of popped popcorn per unit of uncooked kernels, thus reducingthe efficiency of the popping apparatus and raising the cost of theoperation.

While one aspect of the invention herein lends itself to reduction ofthe vagaries of operational and processing circumstances as noted above,it is also noted that it is important for an operator to tend to theprocess at specific times, yet remaining free to handle other choreswhile the popping process is processing. For example, in many poppingsystems, it is desirable and even necessary for an operator to tend toloading the kettle with corn and oil for popping at an appropriate timein the cycle. It is also desirable for an operator to monitor or tocause dumping of popped corn from the kettle at a particular time tokeep it from burning. Yet it is also desirable both that the poppingprocess does not fully engage the operator doing the whole process andthat his attention to the process is positively obtained at such timesas loading and dumping.

In another aspect of the invention, it is recognized that in the past,various improvements in popcorn have been made by popcorn producers inthe science and technology of the corn. These have resulted in improvedtaste, improved kernel expansion rates and more complete popping.Improvement in the popping machines or equipment to produce betterpopped products have not generally kept pace with the improvements inthe corn. While there have been certain improvements in poppers directedto better popped corn products, such as in U.S. Pat. Nos. 5,743,172;5,694,830 and 5,871,792, for example, there is still room for furtherequipment and process improvement to improve the final popcorn product.

In particular and as referred to above, it should be appreciated thatpopped popcorn should not be chewy, should have a high expansion ratiofrom the unpopped kernel, and should have about 12% to about 13% of themoisture of the raw, unpopped kernel. Popcorn meeting these parametersis highly desirable from a taste standpoint. Despite improvements in thecorn kernels, however, these final desirable parameters requireimprovements in popping technology for consistency.

For example, if the moisture content of the kernel is reduced too fastin the popping process, the kernel pops prematurely, resulting in asmall product. On the other hand, if the moisture content of the kernelis reduced too slowly, the hull first cracks, moisture leaks and thepower of the remaining moisture is not sufficient to produce the desiredexpansion of the kernel for the final product. Thus the rate ofapplication of heat to the corn is a factor in producing the mostdesirable popcorn.

In a typical popper, a covered heated popping kettle is generally used.Heating elements are usually mounted on the underside of the kettle andare controlled by a mechanical thermometer between on/off status to heatand pop the corn therein. In one instance, a thermocouple has been used.The elements are disposed on a heat dissipation plate or surface on thekettle bottom and have sufficient output to heat the kettle to a levelin excess of the ultimate temperature desired after popcorn kernels andoil are loaded (which reduces kettle temperature from a control orpreset temperature). The elements produce such excess heat in order toensure that the appropriate popping temperature can be reached is adesired time period.

In other words, when relatively colder corn and oil are added to aheated kettle, the temperature drops, then climbs back to a desiredtemperature so that the kernels are exposed to a quantum of heat duringa period necessary for popping. If the elements were not so powerful,the desired heat may eventually be attained but this could require anexcessive duration of cooking time.

The graph in FIG. 8 of U.S. Pat. No. 5,871,792 demonstrates such apopping cycle. From a cold start with the kettle at an ambienttemperature, the heating elements are turned on to warm the kettle. Itstemperature rises to an “overshoot” level above a “control” level ofabout 525° F. The heating elements are then cycled on and off uponsensing by a mechanical thermometer so that kettle temperature cyclesabove and below the control temperature.

When the unpopped kernels and oil are loaded into the kettle, they areat ambient temperatures, much cooler than the kettle's controltemperature, and act as a heat sink, thus reducing the kettletemperature, such as shown in the graph, down to about 325°, forexample. The mechanical thermometer, for example, eventually sensingthis drop, causes the heating elements to energize to raise the kettletemperature back up toward a temperature where the corn is considered tohave been popped and can be dumped.

There are several areas in which this process could stand furtherimprovement as will now be discussed.

Applicant has determined that an ideal cooking time of from about 3.0minutes to about 3.5 minutes is preferred in order to produce the besttasting popcorn with the highest expansion ratio (largest size).Achievement of this ideal process requires close control of the heatenergy of the kettle. If the initial heat energy of the kettle (i.e.considering kettle temperature and kettle mass) and/or the ability torecover after the corn and oil is loaded (i.e. considering temperature,mass and available wattage of heating elements) is too low or too high,the cooking cycle will be too slow or too fast respectively. When thecooking cycle is too slow or too fast, the popcorn will be too small,chewy and will have too many unpopped kernels.

Moreover, when the popping is first heated from a “cold start”, oninitial turn on, its temperature rise may be rapid, causing it toovershoot and reaching a higher temperature than initially desired.While controllers such as that disclosed in the aforementioned patentscited herein are useful in eliminating excessive overshoot in subsequentcycles, they have not been so advantageous for the initial cold startcycle or the first several popping cycles thereafter before the cookingsystem reaches a heating equilibrium. This can cause undesirable tasteand quality variations in the initial popped corn batches.

In order to fully understand the cooking process and as background forthe invention herein, it is helpful to articulate certain definitions,functions and structure of popcorn poppers. Generally, the kettle is asexplained above and includes a covered heated kettle provided withheating elements for heating a heat dissipation plate or surface on thekettle bottom, and thus the kettle.

Based on the kettle construction, its mass, the materials of the kettle,etc. the power of the heat elements (watts) are determined to permit thekettle to recover from the temperature drop resulting from loading ofthe corn and oil. Then, one of the significant remaining variables isthe temperature of the kettle, which determines the initial heat energyof the kettle. Thus, the “control temperature” (Tcontrol) means apreselected temperature of the cooking or popping surface of the kettle,which the controlling method or apparatus allows the kettle to approachbefore it is shut off in the first cycle from a cold start. The “loadtemperature” (Tload) means the preferred temperature of the cook orpopping surface of the kettle at the time when corn kernels and oil isloaded into the kettle before the temperature drop. The “dumptemperature” (Tdump) means the predetermined temperature of the cook orpopping surface of the kettle when the corn has popped and the kettle isready for dumping the popped corn. Typically in current poppers, Tloadis greater than Tdump by a small percentage.

According to the invention, applicant has determined it is desired toproduce enough heat in the corn to cause it to be popped when the kettlereaches a predetermined ump temperature at about 3.0 to 3.5 minutesafter the kettle is loaded. Thus, according to the invention, the kettleshould be controlled in each cycle such that a predetermined Tdump isreached within the ideal cycle time of about 3.0 minutes to about 3.5minutes from the loading of kernels and oil to dumping of popped corn.This appears to produce the most consistently high quality, good tastingpopcorn, the process of the invention disclosed herein is directed toreaching a predetermined and constant Tdump temperature for allsituations. The potential variations of cooking time based on varyingTload temperature points are shown in the following graphs. These showthe relationship of varied Tload temperatures and the initial heatenergy of the kettle to the popping cycle in time.

FIG. 9 illustrates a situation where Tload is equal to Tdump. FIG. 10illustrates a situation where Tload is greater than Tdump. FIG. 11illustrates a situation where Tload is less than Tdump.

From these graphical illustrations, the following observations can bemade:

First, the overall slopes of the curves are similar, just shifted up ordown. This is because all three graphs assume the same heating elementsand wattage, and the same kettle construction and mass.

Secondly, the popcorn has completed popping at the same Tdumptemperature, independent of the Tload temperature of the kettle when thecorn is loaded. This observation will be described later as one of theimportant concepts contemplated by the invention.

Thirdly, the loading of corn and oil at different Tload temperatureextend or shorten respectively the duration of the cycle until reachingTdump. This inconsistency of Tload most frequently occurs between thefirst or cold start cycle and the subsequent cycles. If kernels and oilare added at that time, i.e. a high Tload temperature, then the cycletime or duration may be too short. If the kernels and oil are added at alower Tload temperature, too much before Tcontrol is reached, then thecycle time is extended beyond that time duration desired.

It will also be appreciated that varying “lag” factors are inherent inprior poppers, and that these lag factors prevent the close control ofkettle energy now desired and which is provided by the invention herein.

Thus, if the Tcontrol temperature and the Tload temperature aremaintained as closely as possible according to the invention, then thecycle duration can be more closely or accurately produced within thedesired cycle time of about 3.0 to about 3.5 minutes.

Given the importance of keeping the Tload temperature substantiallyequal or as close to the Tdump temperature as possible for the bestquality popcorn according to this invention, the challenge is tominimize the normal differences between heat energy imparted to the cornfor the first cold start cycle and for the subsequent cycles. Thedifferences can occur due to at least the following circumstances:

a. The point where the temperature sensor is located is separated fromthe cooking surface. This is related to the mass of the materialsbetween the temperature sensor located on one hand and the cookingsurface. The effect is a time and temperature lag between what thecooking surface temperature actually is, and what the remote temperaturesensor and control “thinks” it is.

b. The surface where the heat elements are located is separated from thecooking surface by the kettle components, which also introduces a timeand temperature lag. When the heat element is turned on or off, there isa lag before the cooking surface begins to react. There is also a smalllag associated with the heat element itself. Thus the mass of materialbetween the heating element and the actual cooking surface, as well asthe rise time of the heat element itself involves an inherenttemperature and time lag.

c. The traditional method of controlling temperature of a popcorn kettlewhich is by use of a “mechanical” thermostat, inaccuracy aside, or evena thermocouple with a set or nonprogrammable control inherent introducesits own time lag related to the mass and mechanical operation of such asensor.

d. And perhaps most importantly, the fact that if the cold start cycleis controlled the same way as subsequent cycles, the initial Tload maybe too low and the duration of that cycle, until Tdump is reached couldbe too long.

The various factors described above are amplified by the fact that thekettle's heat elements usually have far more power than is necessary tosimply hold the kettle at a Tcontrol or Tload temperature. This isnecessary to cook the popcorn in the required time, i.e. to bring up thetemperature of the corn for popping in a desired time. With the lagtimes of many prior poppers, the net effect is a large overshoot ofpreferred control temperature as the kettle at least initially heats oran undershoot if the heat energy is turned off too soon because of anexcessive sensed rise rate. By the time the mechanical thermostat orthermocouple reacts to turn off the heat, the kettle surface temperaturecould exceed Tcontrol by the overshoot. Also, even where a thermocoupleis used, its own heat equilibrium may not be obtained during the firstor first several cooking cycles and the accuracy and dose control of thecooking process desired is not initially obtained. Conversely, beforethe heat element turns on, the temperature will undershoot. The chart ofFIG. 12 demonstrates this operation.

The thermal transients in the system are believed to be one of the mostsignificant of the factors generating this prior profile in thosesystems using such sensors. As mentioned above, there are two majorproblems with temperature sensors related to the effects described.

First, overshoot from a cold start. The operator does not know when toload the corn and oil from a cold start. If he puts the kernels and oilin too early, the quality of the popped corn will be poor. If he waitstoo long, he may “hit” the peak overshoot temperature which will alsocause poor quality popped corn and may cause oil smoke.

When the PID controls heat rise from a cold start, the heat energy maybe turned off too soon, but the lack of heat equilibrium results in lessheat energy in the system and too long or time is required for thekettle to recover to Tdump after its first load.

Secondly, excessive popping cycle times due to low (and also due tohigh) kettle temperatures are undesirable. The low condition is obvious,but a high load temperature actually can cause lengthy popping cycles upto 5 minutes. The kettle's temperature sensor opens due to a hightemperature. The overshoot permits the heat energy of the kettle toincrease further. If the corn and oil are added at this time, the heatenergy of the system falls quickly, but the higher sensed surface heatfrom the overshoot “feeds” the remote mechanical thermostat orthermocouple which keeps it from closing. By the time the heat energy inthe kettle mass between the cooking surface and the remote sensordissipates and the sensor does close and the heat elements are turnedon, the kettle cannot recover to cook the popcorn close to the desiredcycle time.

Accordingly, it is desired to produce a consistently higher qualitypopcorn through improved apparatus and popping processes.

Another objective of the invention has been to reduce popping kettletemperature overshoots and undershoots as a function of systemparameters of prior popping systems.

Another objective of the invention has been to provide a consistentlyhigher quality popped corn by more closely controlling the poppingparameters of the corn poppers than in prior systems.

A yet further objective has been to overcome the information andproblems generated by application of the control logic to both coldstart and subsequent popping cycles.

A yet further objective of the invention has been to provide improvedpopped corn by insuring a consistent popping cycle within the durationof about 3.0 to about 3.5 minutes independently of the coincidence ofthe loading of kernel and oil with the temperature (Tload) for allcycles of the popper.

It is another objective of the present invention to provide improvedapparatus and/or methods to pop popcorn continuously in consecutivebatches with minimal attention by an operator.

It is another objective to ensure that the popcorn is consistently andproperly cooked in each batch.

It is a further objective of the present invention to reduce the burningof popcorn sometimes associated with conventional machines and operatorinattention.

It is also an objective of the invention to always provide the properamount of cooking oil and thus reduce the messes associated with suchburned popcorn or spilled, uncooked oil and thereby allow an operator tofocus upon customers and popcorn sales.

It is a still further objective of the invention to reduce the delaysbetween fresh batches of popcorn attributable to lack of attention bythe operator.

It is a still further objective of the invention to increase theproduction rate of consecutive batches of fresh popcorn to therebyincrease the sales from and the profitability of a commercial popcornpopper.

Still further, it is an objective to provide the proper and consistentheat to the kernels as they cook to ensure proper popping conditions andto maximize the popcorn yield per unit of kernels.

SUMMARY OF THE INVENTION

Addressing these objectives, the present invention comprises a popcornpopper which may be left unattended to automatically cook and dumppopcorn once it has been loaded with the proper ingredients, such asuncooked popcorn. Alternately, features of the invention are alsoapplicable to poppers with manually dumped kettles. The proper,premeasured amount of oil pump is then added by the oil pump system uponthe initiation of a cooking cycle so that the operator does not have toworry about measuring oil or excess oil in the kettle. The popcornpopper of the invention is responsive to kettle temperature conditionsto automatically cook popcorn kernels, subsequently dump the finishedpopcorn, and then alert the operator to load more ingredients such asoil and uncooked kernels, and start the next batch. In that way, all ofthe batches of fresh popcorn are properly cooked at regular periods withthe proper amount of oil and heat, and the operator is left to attend toother tasks.

According to the invention, popcorn is consistently cooked byintroducing an amount of popcorn and oil to a cooking system, comprisinga heated kettle, for a duration sufficient to heat the corn and oil apredetermined amount, and then automatically dumping popped popcornafter a sufficient amount of heat energy has been absorbed by the cornand the oil to pop the corn. The application of heat energy to the cornand oil is not monitored and controlled by time, but rather by the heatconditions of the cooking system for each batch. In this regard, akettle is heated to a start temperature and cycled about thattemperature through a small temperature range. When unpopped corn andoil are introduced, a thermocouple on the kettle senses a temperaturedrop (cycle point) and a cooking or popping cycle begins. The corn andoil absorb the heat energy and are heated in the kettle until the kettletemperature climbs back to a predetermined temperature (dump point)indicating sufficient heat energy has been applied to the corn and oilto pop the corn. At that point, the kettle is automatically dumped.

Since the controller is temperature, rather then time responsive, theoperator is assured a consistent amount of heat is always applied to thecorn and oil for consistent popping. If the kettle dump was controlledby time alone, and the environment changed, such as a cabinet door beingopen, the cooking cycle might time out before sufficient heat energy wasapplied to consistently cook that batch of corn. Moreover, since thestart temperature is held within a narrow predetermined range, the oiland corn will not be prematurely burned and the temperature gradientsapplied thereto will be more consistent. Also, such a methodaccommodates at least some variations in the amount of corn and oilintroduced to the kettle. If too little, the temperature drop will notbe as great and the rise to the predetermined dump temperatures takes ashorter time, thus sufficient but less heat is introduced so this batchis consistently popped. In a corresponding manner, larger amounts ofcorn and oil will slow the climb of temperature to the dump pointinsuring that sufficient heat is imparted to pop the corn consistentlywith other batches.

To further ensure proper cooking by the invention, a premeasured amountof oil is introduced to the kettle at the beginning of a cooking cycle.The controller is coupled to an oil pump system which is operably influid communication with the kettle. Upon the kettle reaching the properstart temperature or cooking temperature, the oil pump system and an oilpump switch are enabled. The operator then actuates the oil pump switchto activate the pump system and deliver a proper, premeasured amount ofoil to the kettle. The oil pump system and switch are disabled by thecontroller if the kettle heat is not ON (no cooking cycle) or the kettleis tilted from an upright position, such as to be cleaned. Furthermore,in accordance with the principles of the present invention, the oil pumpsystem will only deliver one load of oil per cooking cycle to prevent anoil overload or spilling of oil when the cooked batch of popcorn isdumped. Therefore, the oil pump switch may be actuated numerous timesand only one load of oil will be delivered per cooking cycle.

In an alternative embodiment of the invention, the controller isoperable to activate the oil pump system automatically upon theinitiation of a cooking cycle. To that end, the controller provides anoutput signal to the oil pump system to pump a premeasured amount of oilto the kettle at a predetermined time in the cooking cycle. For example,the oil might be added when the kettle has risen to a start temperatureor might be added after the popcorn has been added. If the oil pumpsystem has a mechanically adjusted timer mechanism for pumping apremeasured amount, an output signal is provided by the controller toactivate the pump and pump oil into the kettle. If the oil pump systemincludes a programmable timer mechanism, the controller is operable toprovide additional timer outputs to adjust the amount of time that thepump will deliver oil when activated. In either case, a premeasured andproper amount of oil is delivered to the kettle each cooking cycle. Thecontroller will not activate the pump system until the kettle is hot andready to cook and is upright.

More specifically, the popper apparatus includes a kettle which iscoupled to a dumping motor and a heater which are controlled by acontroller which monitors the kettle temperature. The controllerincludes a temperature sensor, such as a thermocouple, which is operablyconnected to the kettle proximate the heaters. By monitoring thetemperature of the kettle, the controller is operable to dump the kettleat the proper time and to alert the operator when another batch ofuncooked corn kernels should be added to the kettle. Since the kettletemperature is constantly monitored, and the dump cycle is automaticallycontrolled, the burning of popcorn is prevented. Furthermore, anoperator does not have to constantly monitor the procedure to preventsuch burning and can thus turn his attention to other tasks. The popperbegins a cooking or popping cycle when fresh ingredients are added, andby alerting the operator at the end of each popping cycle, the poppereffectively reduces the delay between batches to increase itsproductivity.

In a preferred embodiment of the invention, a programmable logiccontroller (PLC) is coupled to a temperature controller which, in turn,is coupled to a kettle thermocouple and to kettle heaters. When thepopper is turned ON and the kettle heat is turned ON, the kettle isheated to an equilibrium start or cooking temperature of, for example,approximately 525° F. The thermocouple and temperature controllerpreferably maintain the desired 525° F. kettle cooking temperature in asmall cycled range of +/−10° F. When the kettle has reached theequilibrium start temperature, the PLC activates indicators whichprovide visual and audible indications that the kettle is ready to makepopcorn. The oil pump system and pump switch are enabled and theoperator actuates the oil pump switch to load the oil which is pumped inby the oil pump, and also loads the uncooked popcorn kernels.

Alternatively, the oil might be loaded by hand by the operator. In stillanother alternative embodiment of the invention, as discussed above, thePLC provides outputs directly to the oil pump system to automaticallypump oil to the kettle at the initiation of a cooking cycle. The PLC isoperably coupled to the oil pump system to activate the pump for apredetermined amount of time to ensure a premeasured amount of oil. Atimer determines how long the pump runs once activated to ensure theproper amount of oil. The invention may incorporate an oil pump systemhaving a mechanically adjusted timer, such as a dial timer, or mayincorporate a system having a separate programmable timer. In the lattercase, the PLC is operable to provide separate output signals to theprogrammable timer to set the pump time in addition to any outputsignals to the pump for delivering oil for the amount of time set by thetimer.

The temperature controller senses the rapid drop in kettle temperatureassociated with the absorption of heat from the kettle by the corn andoil. When the temperature drop exceeds a set amount, for example, 50° F.below the equilibrium start temperature, the PLC initiates a cookingcycle. The point of initiation of the cooking cycle is designated thecycle temperature or cycle point.

As the cooking cycle progresses, the PLC senses through the temperaturecontroller, that the kettle has dropped to a minimum temperature belowthe cycle temperature. The minimum temperature will depend upon the heatload added to the kettle. As the popcorn pops, the temperature of thekettle begins to rise above the minimum temperature. When the kettletemperature reaches a predetermined dump temperature or dump point andthe PLC that the minimum temperature was previously reached and waspreceded by the cycle temperature, the popper indicates that the end ofthe cooking cycle has occurred. Preferably, the predetermined kettledump temperature associated with the dump point for determining the endof a cooking cycle is equal to the cycle temperature associated with thestart of the cooking cycle, i.e., approximately 50° F. below theequilibrium start temperature, for example. Upon sensing the end of thecooking cycle at the dump point, the PLC initiates a dump cycle andcontrollably energizes the dump motors to tilt the kettle and dump thefinished popcorn onto the surface platform. The popcorn is immediatelyand automatically dumped at the end of a proper cooking cycle, thereforepreventing the popcorn from burning. Furthermore, because of the uniquetemperature-driven control of the popper, the popcorn is consistentlyand properly cooked and may be served at the peak of freshness. Thegreater the amount of corn and oil added, the longer the cooking cycle.Conversely, the less the amount of corn and oil, the shorter the cookingcycle.

Preferably, the motors are controlled to dump the kettle twice to ensurecomplete dumping. After the first dump, the kettle is only partiallyreturned to a cooking or popping position. It is then dumped againbefore fully returning to a popping position.

When the temperature controller indicates that the kettle temperature isbelow the cooking cycle point and the machine is in a cooking cycle, thePLC disables the dump motors and thus prevents inadvertent dumping ofthe kettle contents.

When the popcorn has been dumped at the end of a cooking cycle, thekettle will heat back up to the start cook point again, and audible andvisual indications are again initiated to remind a busy operator toreload the kettle with fresh ingredients. This prevents delays inbetween consecutive batches of popcorn and thus increases the efficiencyof the operator and the popcorn popper, increasing production rates andprofitability.

The present invention provides the proper application of heat energyconsistently to batches of corn kernels. In that way, the kernels areheated to a sufficient temperature to provide proper hull brittlenessand expansion when the kernels pop but the heat is not so high so as toforce out the steam in the kernel prematurely. Therefore, the inventionachieves the desired corn temperature and peak steam pressure for properexpansion. Expansion rates of approximately 1:50 have been achieved withthe invention which is a significant improvement over some conventionaldevices which achieve expansion rates of 1:44 or lower.

Therefore, the present invention automates the cooking and dumping ofpopcorn and eliminates the need for constant operator attention to theprocess. Production of consistently popped corn is increased as is theprofitability of the operation while incidents of burned corn andinadvertently spilled oil or uncooked corn are eliminated. Furthermore,the temperature control of the kettle operation and the cooking cycleprovides properly and consistently cooked batches of popcorn.

An alternative embodiment of the invention contemplates the use of akettle-mounted thermocouple interconnected to an electronic controlsystem for operating the kettle's heating elements, and a differentcontrol logic for the first heat rise of the kettle from a cold startcondition. The thermocouple has negligible mass, is located on thebottom of the kettle, and is connected to the electronic control whichwill control voltage to the heat elements, depending on the desiredthermocouple open and close temperatures. The overshoot and undershootwill thus be significantly less due to the elimination of some lag dueto the use of remote mechanical thermostats in prior systems. Moreover,the control system is programmed to energize and deenergize the heatingelements in response to the sensing conditions of the thermocouple attemperatures which lead to the desired cook surface temperatures as afunction of kettle mass and heating element lags in both directions(i.e. temperature rises and drops). Thus, the thermocouple sensedtemperatures are handled by the control system as a function of thedesired temperatures taking into consideration kettle mass and other lagfactors so the heat energy that the corn kernels experience is closelycontrolled to predetermined levels.

The cold start problems noted above are prevented by directlycontrolling the application of heat to the kettle on the start up,outside of the normal control loop. In particular, heat energy input isnot retarded or controlled so quickly as it is later when the structurehas reached heat equilibrium. Thus, the program for normal operation isvaried for the first cycle to insure that batch is consistently poppedwithin the desired time frame as subsequent batches. The system thenreturns to normal control mode. Thus, the control system recognizes thecold start situation for the first cycle.

In other words, on cold start, the control system logic for remainingcycles is not applied to the kettle heat. Instead, the temperature riseis allowed to continue to a point beyond where it would be allowed torise for subsequent cycles when the kettle has reached equilibrium. Inthis manner, the kettle is allowed to heat to a higher point,recognizing that total heat in the system is less than it will be later.Thus, when corn and oil are added and the temperature drops, the higherstart temperature supports the kettle's recovery to a Tdump temperaturein a similar time frame to that of subsequent cycles. Without the“override” of the control logic for the first cold start cycle, the heatenergy would be retarded sooner and corn loading would drop the colderkettle to a much lower temperature than desired, from where it couldtake an excessive time to recover.

The chart of FIG. 13 illustrates the contrast between the invention andthe prior systems.

It will be appreciated that Tdump, according to the invention, isconstant and independent of Tload. According to the invention, Tdump isindependent of many other variables, including:

Low voltage, which reduces the power of the heat elements.

Variations in the amount of corn and/or oil that are added to thekettle.

Variations in the kettle components: heat elements, etc.

The system is thus controlled that, given the same Tdump, temperaturepopping time will vary only within the desired cycle time of about 3.0to about 3.5 minutes for every cycle.

In another aspect of the invention, and even where an automatic dumpmode is or is not selected, or in other poppers where there is noautomatic dump mode, the electronic control system is operable to soundaudible or visual alarms, such as a buzzer or flashing light, to alertthe operator to dump the popcorn at the correct time. Also, such alarmsare programmed to alert the operator to do one of the following threethings according to the invention:

1. From a cold start, an alarm signals when the operator should firstadd the corn and oil.

2. When popping, an alarm signals when to dump the popcorn. The largerbenefit is the fact that it alerts the operator, who is busy ordistracted, to dump the popcorn before it burns. Burned popcorn is asignificant problem in a busy theatre, for example.

3. When the operator is done popping corn, an alarm reminds him to turnoff the master power to the kettle heat to save energy.

The invention also contemplates the process of producing popcorn bypopping corn kernels in oil for a time period of about 3.0 to about 3.5minutes from loading kernels and oil into a popping kettle to dumpingpopped corn therefrom. That is, the invention contemplates the poppingof popcorn in a time duration from loading kernals and oil into a kettleto dumping popped corn therefrom in a time period of from about 3.0 toabut 3.5 minutes and after a set Tdump temperature is reached,regardless of typical variations in the quality of corn and oil added byoperator error and variations in the Tload temperature between coldstart and later cycles.

According to the invention, a preset Tcontrol temperature thus defines amaximum Tload for the first cold start cycle and thereafter forsubsequent cycles, function as a safety or cutoff temperature, causing asystem shutdown when reached for review and safety considerations.

Advantages of the invention are numerous. It produces a high quality,consistent, popped product. It eliminates lag times of the priortemperature sensors used in prior popping systems. It reducestemperature overshoots and undershoots from a desired controltemperature. It assures a predetermined cycle time within a set rangeand with a consistent product. It produces a high quality consistentproduct independent of variables inherent in prior systems which limitproduct consistency. It provides a close control of popping parameters,including close control of kettle energy to produce a non-consistentlyhigh quality product.

It will also be appreciated that the invention in its alternateembodiment can be used in controlling only the initial cold start cycledifferently from the subsequent cycles or the first several cycles froma cold start in the same way, differently from remaining cycles whenheat equilibrium is reached.

These and other objectives and advantages will become readily apparentfrom the following detailed description of preferred and alternativeembodiments of the invention, and from the drawings in which:

BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description of the embodiments given below, serve toexplain the principles of the invention.

FIG. 1 is a perspective view of a popcorn popper apparatus in accordancewith the principles of the invention;

FIG. 1A is a perspective view of the top of the popcorn popper of FIG.1;

FIG. 1B is perspective view of the popcorn popper of FIG. 1 illustratingthe oil pump system.

FIG. 2 is a cross-sectional view of a popcorn popping kettle as seen online 2—2 of FIG. 1;

FIG. 3 is a cross-section taken along lines 3—3 of FIG. 2;

FIG. 4 is a perspective-view of the kettle of the popcorn popper of FIG.1;

FIG. 5 is a perspective view of the kettle of FIG. 4 removed from itshousing for cleaning;

FIG. 6 is a diagrammatic view of the electrical components of thepopcorn popper of FIG. 1;

FIG. 7 is an operation flowchart of the popcorn popper apparatus of theinvention;

FIG. 8 is a temperature graph versus time of the kettle during a popcorncooking cycle.

FIG. 9 is a graphical illustration of a popping process where Tloadtemperature is equal to a set Tdump temperature and shows the effect ontime;

FIG. 10 is a graphical illustration of a popping process where Tloadtemperature is greater than the set Tdump temperature and shows theeffect on time;

FIG. 11 is a graphical illustration of a popping process where Tloadtemperature is less than the set Tdump temperature and shows the effectson time;

FIG. 12 is a graphical illustration showing a popping process of theprior art;

FIG. 13 is a graphical illustration showing kettle surface temperaturecycles of a popping process of one embodiment of the invention comparedto those of a prior popping system;

FIG. 14 is a diagrammatic view of the electrical components of a popcornpopper similar to FIG. 6 but according to an alternate embodiment of theinvention; and

FIG. 15 is an operational flow chart similar to FIG. 7 but illustratingan alternative embodiment of the invention.

FIG. 16 is a temperature graph versus time of the kettle during popcorncooking cycles for another embodiment of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Turning now to the drawings, there is shown in FIG. 1 an automated cornpopper 10 according to the invention. It will be appreciated that thepopper is operable to cook or to pop popcorn and is particularly usefulfor cooking consecutive batches of popcorn for sale for use byconcessionaires at movie theaters, sport events, fairs and the like.

The corn popper 10 includes a cabinet having transparent walls includingtwo sidewalls 11, 12, a rear wall 13, front wall 14, and a serviceplatform 17 for catching popcorn. Front wall 14 includes two doors 15,16, which can be opened to gain access, both to the popped corn on theplatform 17 of the cabinet and to the kettle 18. Sidewalls 11, 12 andrear wall 13, as well as the front wall 14 including doors 15, 16, areall made preferably of transparent glass or plastic material so that theinterior of the cabinet can be viewed from the exterior. The cabinet mayalso include various operating switches and light indicators on anoperating panel 25 for turning ON kettle heat, the dump motor, a warmer(not shown) under platform 17 and lights inside the cabinet as well asturning ON the heaters and pumps of an oil pump system (see in FIG. 1B)for providing cooking oil for the operation. The lights may indicatethat one or more of these systems are ON. Various of these systems willnow be described in greater detail in accordance with the principles ofthe present invention.

The cabinet of popper 10 also preferably includes an oil pump system 36which would rest below the platform in the cabinet (see FIG. 1B). Theoil pump system 36 provides oil to the kettle during a cooking cycle andmight be one of various different systems. For example, Gold MedalProducts Co. of Cincinnati, Ohio, which is the owner/assignee of thepresent patent application, markets the Model 2114 Accumeter Bucket Pumpfor pumping popcorn oil. Another system, Model 2257 Rack Oil DeliverySystem, is also available from Gold Medal Products and is discussed inU.S. patent application Ser. No. 08/541,469 entitled “Oil Supply forPopcorn Poppers”, which application is incorporated herein by referencein its entirety. While those oil systems manufactured by Gold MedalProducts Co. are preferable, the present invention might be utilizedwith other systems as well.

The popping kettle 18 is of any suitable variety having a heater (notshown in FIG. 1) interconnected by a control line 19 to a power plug 20mounted inside on the top 21 of the cabinet. It will be appreciated thatthe kettle 18 is tiltable about a tilt axis 22 (FIG. 2) and is providedwith covers 23 and 24 which are pivoted on the kettle 18. When the cornis popped, it pushes these covers open and falls out the sides of thekettle onto platform 17. Moreover, it will be appreciated that the cover23 is located over a so-called “dump section” or side of the kettle 18.When the kettle is tilted, this cover pivots open to facilitate dumpingof popcorn onto platform 17.

Positioned between covers 23, 24 is an oil funnel 29 which has a flaredfunnel mouth 30. When the kettle 18 is upright as shown in FIG. 1, thefunnel 29 aligns with an oil outlet 37 which is coupled via a deliverytube 39 to oil pump system 36. Oil is pumped up by system 36 to draininto funnel tube 29 and kettle 18 for use during a cooking cycle asdiscussed in greater detail hereinbelow.

The kettle 18 includes an internal agitator, stir blade or rotor 38(FIG. 3) driven by a rotor drive shaft 26 having an upper pilot end 27and a driven gear 28 thereon. Referring to FIG. 4, when the kettle is ina cooking position as shown in FIG. 1, the upper pilot end 27 of therotor drive shaft 26 is located in a socket 31 defined in a rotor drivehousing 32 adjacent a drive shaft 33 and a drive gear 34. The drive gear34 intermeshes with the driven gear 28 on the upper pilot end 27 of therotor drive shaft 26 to drive the rotor within the kettle to promotepopping. Directly above socket 31 in drive housing 32 is a positionsensor 35 which determines that shaft 26 is seated in socket 31 andkettle 18 is in a cooking position. The sensor 35 promotes more accuratepositioning of the kettle after it is tilted as discussed in greaterdetail below. The stir blade and shaft 26 are rotated by stir motor 68which is activated by an appropriate operating switch on the panel 25 orby the controller of the invention as discussed below.

Referring again to FIG. 3, the blade 38 of the invention is weighted toprevent popcorn from being trapped against the blade during a dumpcycle. As discussed further hereinbelow, the kettle 18 is tilted ordumped during a cycle to dump out the cooked popcorn. To preventhindrance of the popcorn by blade 38, the blade is weighted on one sidewith an appropriate weight element 47 which causes the blade to rotateto a downward or generally vertical position during a kettle dump cycle.The blade 38 is then out of the way of the dumped popcorn so thatpopcorn falls freely from the kettle.

The kettle is mounted in the cabinet of the popper 10 by way of a drivehousing 40 and a spring-like hanger bracket 41. The spring-like hangerbracket 41 includes an L-shaped bracket having a foot 42 forinterconnection to the top 21 of the cabinet. The depending flat springleg 43 is provided with an aperture or slot 44, as will be furtherdescribed.

On the other side of the kettle, the drive housing 40 houses the driveshaft 48, which is provided with a worm gear 49 on the bottom endthereof. A drive stub shaft 50 is provided with a gear 51 forintermeshing with the worm gear 49. The opposite end of the drive stubshaft 50 is provided with a drive stub 52 disposed in a socket 53 of thedrive housing 40. The upper end of the drive housing 40 is provided witha mounting foot 54 for securing the drive housing 40 to the top 21 ofthe cabinet of the popper 10. In addition, it will be appreciated thatthe drive shaft 48 can be a one-piece drive shaft or it can be coupledthrough a coupling 55 to the depending drive shaft 56 of a dump motor 58(FIGS. 1 and 1A). Drive shaft 48 is journaled in a blind bore 45 locatedin an externally threaded bushing 46 in the bottom of housing 40 (FIG.3). This prevents lubricants from leaking into the popped pop corn.

The kettle 18 is provided with a drive boss 60 and a hanger boss 61. Thedrive boss 60 is provided with a slot 62 for receiving the drive stub52, supported by the drive housing 40. The hanger boss 61 extends fromthe other side of the kettle with respect to the drive boss 60 and isprovided with a groove 63 for receiving the depending leg 43 of thehanger bracket 41. In this regard, the groove 63 fits within a slot oraperture 44 of the hanger bracket 41 so that the kettle can be rotatedabout the pivot axis 22. At the other drive side of the kettle, thedrive boss 60 resides in the socket 53, defined by the drive housing 40,so that the drive boss 60 can rotate in that socket. It will beappreciated that the socket has an opening 64 for accommodating radialmovement of the drive boss 60 with respect to the socket and to thedrive stub 52 when the drive stub 52 and the recess 62 in the drive boss60 are aligned with the opening 64 to permit the drive boss to be movedoutwardly of the socket.

Alternatively, the kettle could be supported in a cantilevered fashiononly by the drive boss or other supporting apparatus as will beappreciated.

Turning now momentarily to FIG. 1A, there is shown a perspective view ofthe top of the popper 10 showing various components of the poppermounted outside the cabinet on the top 21 thereof including parts of thekettle operating system. The kettle operating system as it is termedherein includes the kettle heaters (not shown) and the kettle dump motor58 as well as the control components which operate the popper inaccordance with the principles of the invention.

As shown in FIG. 1A, the dump motor 58 is mounted on the top 21, suchthat drive shaft 56 extends downwardly through the top 21 and into thedrive housing 40 (FIG. 3). A rotor drive motor or stir motor 68 is alsopositioned on the top 21 so that its drive shaft 33 extends downwardlythrough the top 21 and through the housing 32 for interconnection withthe drive gear 34. A buzzer 70 is positioned preferably on the top 21 asshown, as well as a cabinet light 75, a ventilator 76 and varioussupport circuitry for the components, including a Programmable LogicController (PLC) 77, a temperature controller 82, and a solid staterelay 86 to the kettle heaters.

The control components for the control system of the invention comprisea Programmable Logic Controller, or PLC, such as a PLC made by OmronElectronics, Inc., One East Commerce Drive, Schaumburg, Ill. 60173,under the Model No. C20R. PLC 77 is connected to dump motor 58 throughan UP relay 78 and a DOWN relay 79. The PLC is also connected to theaudible buzzer 70 and to light 71 for audibly and visually notifying anoperator when the kettle 18 is ready to receive another batch ofpopcorn, oil, salt and other ingredients. The visual indicator light 71,which may be positioned on control panel 25, flashes to visually alertan operator that the kettle is ready for another batch of ingredientssimultaneous with the buzzing of buzzer 70. The visual indicator light71 will provide a visual indication to an operator and is particularlyhelpful in the case of multiple machines in an area where it may bedifficult to determine which one is buzzing. The PLC 77 provides outputsignals to the dump motor relays 78 and 79 to tilt the kettle and dumpthe popcorn cooked therein at the cessation of a cooking cycle. Outputsignals from the PLC 77 to the buzzer 70 and light 71 produce an audiblesignal and a visual signal which ensure consecutive batches of freshpopcorn without delays between batches as are normally associated withconventional popcorn machines.

The present invention is operable to monitor the temperature of thekettle to automatically alert the operator to load ingredients toautomatically begin a cooking cycle when ingredients are loaded, and toend the cooking cycle and automatically initiate a dump cycle to emptythe popcorn and again alert the operator to load more ingredients forthe next batch. The invention monitors the kettle temperature anddetermines at certain temperature checkpoints which operations are to beautomatically executed. Therefore, the popper of the invention may beloaded with corn and/or oil and then ignored until the next ingredientsload to free the operator to handle other tasks. To that end, thecontrol system of the invention further comprises a temperaturecontroller 82 to control the heating of kettle 18 and to provide inputsignals to the PLC 77 for initiating a popcorn cooking cycle andsubsequently for controlling dump motor 58 to dump finished popcorn fromthe kettle after a cooking cycle is complete. The temperature controller82 has an output line 84 which is operably coupled to a solid staterelay 86 connected to kettle heater 88. To provide a temperature inputto the PLC, a thermocouple 90 is operatively connected to kettle 18close to kettle heater 88 to monitor the temperature of the kettle. Anoutput signal on line 92 from the thermocouple is input into thetemperature controller 82. Through thermocouple 90 and line 92, thetemperature controller 82 monitors the temperature of kettle 18 andturns power to the heater 88 ON and OFF through solid state relay 86 tomaintain the temperature at a predetermined start temperature orequilibrium temperature. Preferably, the start temperature isapproximately 500° F. to 525° F., although it will be appreciated by oneof ordinary skill in the art that such a temperature might be varied upor down for a particular size kettle or other variable cookingconditions.

The temperature controller 82 communicates on line 94 directly with thePLC 77. Line 94 is a low temperature alarm line which is utilized to setthe beginning of the cooking cycle and to initiate a kettle dump at theend of the cooking cycle. As described further hereinbelow, temperaturecontroller 82 sends an input signal on line 94 to the PLC 77 whenthermocouple 90 indicates that the kettle temperature has dropped belowa predetermined temperature or low alarm temperature, such as whenuncooked popcorn kernels and oil are poured into the kettle 18, andthrough thermal loading, cause a rapid decrease in the kettletemperature. The falling temperature passing through the low alarmtemperature point 149 indicates that a cooking cycle has been started(See FIG. 8). As may be appreciated, as the popcorn in kettle 18 cooks,the thermal load is reduced and the temperature of kettle 18 begins torise again. The kettle temperature will again pass through the low alarm150 temperature point, except this time as a rising temperature ratherthan a falling temperature, the rising temperature passing through thealarm point indicates the end of the cooking cycle (See FIG. 8). At sucha time, a signal is sent on line 94 to the PLC 77 to initiate a kettledump procedure to dump the cooked popcorn onto service platform 17 asdiscussed below. While the low alarm temperature may be variablyadjusted in temperature controller 82, it is preferably set to beapproximately 50° F. to 75° F. below the start temperature referencedabove, e.g., it may be set to be approximately around 425°-500° F.,depending upon the preferred start temperature. The temperature pointindicating the temperature 149 as it first falls through the low alarmtemperature when uncooked popcorn is added to the kettle is designatedthe cycle temperature or cycle point as it indicates to the PLC thebeginning of an official cooking cycle. A cooking cycle is not begununtil the kettle drops below the cycle temperature 149 to prevent falsecycles which might occur as the empty kettle fluctuates around the starttemperature (see FIG. 8). That is, the substantial drop from the starttemperature will indicate that corn and oil have been added to thekettle. The subsequent point 150 wherein the temperature increases backup to the low alarm temperature after the popcorn is cooked and poppedis considered the dump point or dump temperature because the PLCinitiates a kettle tilt to dump the popcorn at that temperature.Preferably, the cycle temperature 149 and 150 and dump temperature areapproximately the same (see FIG. 8), e.g., approximately 475° F.However, it may be appreciated that the temperatures might also beoffset from each other. Both the cycle temperature and dump temperatureare below the start temperature point.

In order to ensure stable heating of kettle 18, the temperaturecontroller 82 will preferably cycle solid state relay 86 and heater 88ON and OFF numerous times as the kettle temperature closely approachesthe equilibrium start temperature. This reduces substantial conditionsbeyond levels 142 and 152 of the kettle temperature which might occurshould the heater be turned OFF only at the time that the kettle reachesthe start temperature due to thermal transients in the system. Asuitable temperature controller for use with the invention is the Model935 Proportional Integral Derivative or PID, programmable temperaturecontroller available from Watlow, 1241 Bundy Blvd., P.O. Box 5580,Winona, Minn. 55987-5580. The Model 935 temperature controller 82 iscapable of monitoring when the kettle temperature is getting close tothe equilibrium start temperature and operably slowing down the heatingprocess as that start temperature is approached. The Model 935temperature controller also has an alarm silence feature which preventskettle dumping when the kettle is heating up upon initial powerup. Forexample, as discussed above, temperature controller 82 monitors a risingtemperature which reaches the predetermined low alarm temperature inorder to indicate the end of a cooking cycle and to control the dumpmotor 58 to dump the kettle. As may be appreciated, a rising temperaturepassing through the low alarm temperature is a scenario which will occurupon initial powerup as the kettle heats from a cold state to anequilibrium start temperature. In order to prevent a kettle dump atinitial powerup, temperature controller 82 has a start override featureto ignore the first rising pass 151 through the predetermined low alarmtemperature (See FIG. 8).

As the temperature controller 82 monitors the kettle temperature, itcontrols the operation of the heater 88 through solid state relay 86.The present invention alerts an operator when the kettle is ready tocook, and to indicate to the PLC 77 when kettle temperature has reachedthe equilibrium start temperature, a slave relay 96 is coupled to theoutput of relay 86 and provides an input to the PLC 77 on line 93. Whenthe solid state irelay 86 is closed to provide power to the heaters 88to heat kettle 18, a 24V signal is delivered to PLC 77 through slaverelay 96. When the solid state relay 86 closes and turns power to heater88 OFF and remains OFF, indicating that the kettle has reached starttemperature, (e.g., 525° F.) the slave relay 96 stops the signal to thePLC 77 and the PLC, in response, provides an output to buzzer 70 andlight 71 to produce an audible and visual indication and alert theoperator that the kettle is ready to cook popcorn. With consecutivebatches of popcorn, buzzer 70 and light 71 will again be energized toprovide an audible and visual indication indicating that the popcorn hasbeen cooked and dumped and the kettle is ready for another batch ofpopcorn kernels. In that way, consecutive batches are made withoutdelay.

The PLC 77 is also coupled to the kettle heat switch 80 to monitor whenthe kettle heat to popcorn popper 10 is turned ON and OFF. When power tothe kettle heater 88 is turned OFF, the PLC 77 will internally reset astatus bit. Thus, the PLC is not fooled into initiating a kettle dumpwhen the power is turned OFF and then ON again, and in that way, the PLC77 further prevents inadvertent dumping. For example, when the power andthe heat to the kettle are turned ON by turning on switch 80 to deliverpower to relay 86, the PLC 77 monitors the kettle temperature throughtemperature controller 82. If the heat 80 is then turned OFF, kettletemperature would drop, simulating thermal loading of the kettle withfresh popcorn and oil when indeed no popcorn or oil is loaded. If thekettle heat is then again turned ON, the PLC 77 may note the risingtemperature passing through the low alarm temperature point and thus maybelieve that a batch of popcorn has been cooked and that it is time todump the kettle. By resetting the PLC 77 status bit upon an interruptionof power to the heater 88, such a scenario is avoided. A high limitswitch 98 is coupled to the kettle heater 88 to cut off the power to theheater if the kettle temperature exceeds a set upper limit, such as ifthe solid state relay 86 stays open or the temperature controllermalfunctions.

The stir motor 68 turns a blade (not shown) during the cooking of thepopcorn. In one version of the invention, stir motor 68 is turned on bya switch at the operating panel 25 and stays on. Alternatively, power tothe stir motor is routed through PLC 77 and is controlled by PLC 77 asnoted by line 73. PLC 77 operates the stir motor 68 so that the bladestirs automatically only during a cooking cycle and stops when thecooling cycle is complete independent of operator attention.

The oil for cooking the popcorn may be delivered either by hand, by theoperator actuating a switch on the operating panel 25 which is coupledto pump system 36, or alternatively may be handled automatically throughPLC 77 to automatically deliver oil at the initiation of a cookingcycle. Oil pump system 36 preferably includes a reservoir 101, a controlhousing 103, and a pump 104 to pump oil from the reservoir. The pumpsystem 36 will also usually include a heater (not shown) for heatingcongealed oil to a liquid state before pumping. The heater may beoperably coupled to the control panel so that the oil may be properlyheated for being pumped to kettle 18.

In one embodiment of the invention, the oil pump 104 is operably coupledto an oil pump switch 106 which is located at the operating panel 25.When the kettle heat switch 80 is ON and the kettle heats to the starttemperature, oil will be needed for a cooking cycle. In accordance withthe principles of the invention, oil pump switch 106 will be effectivelydisabled until all conditions are proper for a cooking cycle. Switch 106is operably coupled to PLC 77 as indicated by line 111 and the PLC 77 isoperably coupled to oil pump 104 as indicated by line 113. PLC 77disables switch 106 until the kettle heat switch 80 is ON, as indicatedby control line 115 between switch 80 and PLC 77, until kettle 18 isupright, as indicated by proximity switch 35 coupled to PLC 77, anduntil kettle 18 is properly heated as indicated by the thermocouple 90and controller 82. This prevents oil from being pumped to funnel 29 fromreservoir 101 until the kettle is hot and in the proper position.

Upon enablement of the oil pump switch 106, the operator may engage theswitch to deliver a premeasured amount of oil from reservoir 101.Generally, pump 104 will be controlled by a timer 129 (see FIG. 6) whichmay be adjusted by a mechanically adjusted dial 117. In that way, thepump 104 will pump oil to kettle 18 for a predetermined amount of timeto deliver the proper premeasured amount of oil. When the timer 129times out, the pump 104 stops. Upon delivery of the oil, PLC 77 willdisable switch 106 so that no more oil may be added until the nextcooking cycle. In that way excess, uncooked oil is generally not presentin the kettle, thus preventing any spills or messes. Pump 104 is coupledto line 39 for oil delivery.

FIG. 1B illustrates the oil pumping system which is the subject of U.S.patent application Ser. No. 08/541,469 and greater detail about theoperation of the system is given therein. Pump system 36 is usuallyreferred to as a bag-in-box system and includes a container 118 on topof control housing 103 which holds a flexible bag of oil 121. An oiltube 123 connects bag 121 and reservoir 101. Alternatively, an oilbucket or pail system, such as the Model 2114 Accumeter Bucket Pump (notshown) may be used.

In an alternative embodiment of the invention, the PLC 77 is operablycoupled to pump 104 and timer 129 by control lines 131, so that deliveryof oil is automatic. When the kettle 18 heats up, and is in the properupright position as discussed hereinabove, the PLC 77 will automaticallyactuate pump 104, instead of enabling switch 106 and requiring theoperator to actuate the switch 106. Therefore, oil is deliveredautomatically at the beginning of a cooking cycle. The operator thenonly has to add popcorn kernels, as the cooking cycle begins. Timer 129will control how long pump 104 runs once it is actuated to deliver theproper amount of oil. Timer 129 may be a programmable timer which is setby the PLC 77 control lines 131 and may be programmed for certain,preselected amounts of oil for a batch. That is, the PLC 77 controls thetimer 129 as opposed to a mechanical mechanism such as dial 117. Oncethe timer 129 times out, pump 104 stops and will not be reactuated untilthe next cooking cycle. As with the previous scenario, if the kettleheat switch 80 is OFF, no oil is added to the kettle.

It will be understood that various combinations of oil loading stepsmight be utilized in accordance with the principles of the invention.For example, the oil pump 104 may require switch actuation while thetimer 129 is automatically programmed by PLC 77. In another version, thepump 104 may be automatically actuated by PLC 77 while timer 129 ismanually set by a dial 117 or other mechanical device. The oil system 36will generally include a preheater (not shown) for liquefying the oilprior to pumping. The preheater may be actuated at the control panel 25or directly at the control housing 103 of oil system 36.

As the popcorn and oil are cooked during the cooking cycle and thekettle temperature begins to rise, it rises through the low alarmtemperature 150 point or dump point as discussed above. A kettletemperature rise through the low alarm point or dump point which waspreceded by a cycle point indicates the end of a cooking cycle and theinvention is then operable to initiate a dump cycle. At the initiationof the dump cycle, the PLC 77 actuates the DOWN relay 79 to direct thedump motor 58 to rotate the kettle downwardly and thus dump thecontents. The down relay is actuated for a predetermined period of timeand then the relay is deactuated. Assuming that the cooking position ofthe kettle as illustrated in FIG. 1 is 0°, the kettle is rotatedapproximately 180° for the first dump to dump the popcorn contentstherefrom. That is, the kettle is turned upside down. Subsequently, thePLC 77 actuates the UP relay 78 to energize dump motor 58 and move thekettle 18 toward the cooking position. However, the UP relay is onlyactuated to return the kettle partially to its cooking position and infact is preferably energized for a time period sufficient to move thekettle to an approximately 60° angle between the 0° cooking position andthe dump 180° position. This partial return is obvious to the operatorand prevents him from believing the kettle is in the cooking position.Therefore, the operator is not misled into prematurely loading popcornand oil into the kettle.

After the partial return toward the cooking position, the DOWN relay 79is again actuated to make the dump motor 58 rotate the kettle downwardlyto 180° to again dump the popcorn contents. The two-stage dump cycle ofthe present invention provides proper and complete dumping of all thecontents from kettle 18 so that little or no popcorn remains in thekettle to be burned during the next cooking cycle. After the seconddump, the UP relay 78 is actuated to energize dump motor 58 to returnthe kettle to the upright cooking position. Thus, the kettle 18 isrotated to a full dump position, partially returned, rotated to a fulldump position again, and then fully returned to the cooking position foranother cooking cycle.

Referring again to FIG. 4, when kettle 18 is returned to the cookingposition, the upper pilot end 27 of drive shaft 26 engages socket 31,and in doing so will actuate the proximity switch 35. Proximity switch35 is preferably a metal detecting proximity switch which indicates thepresence of the shaft end 27. Upon sensing the shaft end 27, theproximity switch 35 provides an input to PLC 77 which thensimultaneously actuates both the UP and DOWN relays 78, 79 to lock thedump motor 58 and provide a secure stop when the kettle is returned tothe cooking cycle. Proximity switch 35 provides secure placement of thekettle in the cooking position and allows rapid return of the kettle tothat position without slowing the motor down as the kettle approaches.The present invention thereby prevents overshoot of the shaft end 27 andsocket 31 and also ensures that the gears 28 and 34 are properly seatedfor the next cooking cycle. The proximity switch also ensures that oilcan be added to the kettle 18 only when the kettle is upright.

Upon the return of the kettle 18 to the cooking position with the kettleheated back up to the start position, PLC 77 again actuates buzzer 70 toprovide an audible indication to the operator that another batch ofingredients should be added to the kettle. In that way, consecutivebatches of popcorn are made with very little delay between the batches.Thus, the productivity of the operator and the popper 10 and theprofitability of the entire operation, is increased. PLC 77 operates toactuate buzzer 70 at ten second intervals until new ingredients areloaded into the kettle 18. In that way, the operator cannot ignore thepopper 10 of the invention as it will continue to alert him untilanother batch of ingredients is loaded. If the buzzer is ignored for tenminutes, it will begin to sound continuously.

Kettle 18 may also be removed and cleaned as described in the parentapplication entitled AUTOMATED CORN POPPER referenced above. To thatend, the PLC 77 is operably coupled to a clean switch 99. When the cleanswitch is actuated, PLC 77 is operable to actuate the DOWN relay 79 anddump motor 58 to tilt the kettle 18 to a position between the cookingposition and the full dumping position. In this intermediate position,the plane of the drive stub 52 is aligned with the opening 64 and thesocket 53, thereby permitting the drive bar 60 of the kettle to belifted out of the socket, cleaned, and then subsequently replaced forfurther popcorn cooking as illustrated in FIG. 5.

Further understanding of the present invention may be obtained by adiscussion of the operation of the invention and particularly tooperation of PLC 77. An operational flowchart is illustrated in FIG. 6.

Prior to beginning a cooking cycle or in order to clean the kettle, theheat switch 80 should be OFF (block 95). The PLC 77 then checks to seeif the kettle is cool (block 100). If the kettle is cool, the cleanswitch 99 is enabled by the PLC 77 (block 102). The clean switch maythen be actuated to tilt the kettle 18 for cleaning. The kettle is thencleaned and returned to the upright position (block 127). As will berecognized, the kettle does not always have to be cleaned, and anoperator may proceed directly to a cooking cycle wherein the processbegins at block 105.

To begin a popping operation, the operator turns on the various systemsof the popper. For example, the operator would turn ON the heat switch80 to the kettle heater 88 to deliver power to kettle heater 88 throughthe relay 86. If necessary, the kettle stir motor 68 would be turned ONat panel 25 or may automatically be controlled by the PLC 77. The oilpump system 36 and any components, such as an oil preheater, might alsobe turned ON as indicated by block 105. When the kettle heat switch isON, the PLC 77 monitors the kettle temperature through temperaturecontroller 82 as indicated at block 107 in FIG. 7. As the PLC 77monitors the temperature, it continuously checks to determine if thekettle temperature has risen to the low alarm temperature point whichmay indicate either that the kettle is initially heating up or isreturning to its equilibrium start temperature after having cooked abatch of popcorn (see block 108). As indicated by line 109, the PLC 77will continue to monitor the kettle temperature until it has risen tothe low alarm temperature point. When it has reached the low alarmpoint, as indicated by line 110, the PLC 77 determines whether thesystem is initially being powered up and has not yet cooked the firstbatch of popcorn (see block 112). As discussed hereinabove, thetemperature controller has a start override feature which ignores thefirst rising temperature pass through the low alarm temperature whichindicates that the system is initially being powered up. By ignoring thefirst low alarm temperature point, the dump cycle is not initiated asindicated by block 114. Otherwise, when the rising temperature returnsto and passes through the low alarm temperature point, a dump cyclewould normally be initiated according to block 116 because a low alarmtemperature point preceded by another low alarm point (cycle point) willindicate the end of a cooking cycle and a dump point as described above.

As the PLC 77 and temperature controller monitor the kettle temperature,the PLC 77 checks to see if the kettle temperature has risen to theequilibrium start temperature which is preferably approximately 500° F.to 525° F., as indicated by block 118. If the kettle temperature has notreached the start temperature, the PLC 77 continues to monitor thekettle until that temperature is reached according to line 119. When theequilibrium start temperature has been reached, the system indicatesthat the kettle is ready to be loaded with ingredients to cook a batchof popcorn (line 120). At the start temperature, a buzzer is sounded anda light flashed intermittently by the PLC 77 to notify the operator thatit is time to load popcorn ingredients and to start cooking according toblock 122. The buzzer will sound intermittently at ten second intervalsand will continue to sound for ten minutes. If the operator ignores thebuzzer for ten minutes, and no ingredients have been loaded, the buzzerwill then sound continuously.

When the kettle is ready to cook, the PLC 77 checks to see if the kettleis upright (block 130). If not, the buzzer sounds continuously (block132). If the kettle is upright, the oil pump switch 106 is enabled(block 134). At this point, the oil pump switch 106 may be manuallyactuated to add a premeasured amount of oil to the kettle as describedabove (block 135). After oil is added, the switch 106 will be disabledas discussed above, so that no more oil may be added until the nextcooking cycle. Alternatively, the PLC 77 may automatically actuate theoil pump system (block 137) as described above. At that point, popcornis also added to initiate a cooking cycle. As may be appreciated, theautomatic pumping of oil may be prevented until after the popcorn isloaded and a cooking cycle is initiated, as shown by block 139. In thatway, oil introduction is not premature, such as when the kettle heatswitch is turned OFF while the buzzer is sounding and light flashing toclean the kettle as discussed above. For example, oil might not beautomatically added until after the temperature of the kettle full ofpopcorn drops, indicating the initiation of a cooking cycle.

The PLC 77 then monitors the kettle temperature in order to determine ifthe ingredients have been loaded. As discussed above, the uncookedingredients such as corn and oil will act as a heat load and reduce thekettle temperature when they have been placed therein. As noted in block124, the PLC 77 will continue to monitor the kettle temperature and ifno ingredients have been loaded, i.e., kettle temperature has notdropped (line 125), the buzzer will continue to sound. If ingredientsare loaded, the kettle temperature will drop somewhat rapidly and willplunge below the low alarm temperature point (cycle point) 149 of thetemperature controller (see FIG. 8). The buzzer then stops buzzing andthe light stops flashing. Popcorn is then cooked by the kettle (block128).

As the buzzer 70 is sounding and light flashing 71, the operator has thealternative options of turning the machine off or loading ingredients.If the kettle heat switch 80 is turned OFF, the system operationessentially returns to block 95 to determine if it is safe to clean thekettle.

Returning now to block 128, as the popcorn is cooked, the kettle beginsto again heat up and the temperature controller 82 and the PLC 77continue monitoring the kettle temperature to determine if it hasrecovered or risen back up to the low alarm temperature point (dumppoint) 150 and proceeded through that point on its way back to anequilibrium start temperature (block 108). If the kettle temperature hasrisen to the dump point and it is not an initial power-up situation, asindicated by line 136, a dump cycle will be initiated as describedhereinabove (block 116). After the dump cycle is initiated, the systemeither returns to block 95 if the kettle heat switch is turned OFF toclean the kettle (line 138) or will continue to heat the kettle up toits equilibrium start temperature and will be ready for the next load ofingredients to cook the next batch of popcorn. As illustrated by block118 when the start temperature has again been reached, the buzzer willagain sound to notify the operator to load ingredients. Also, the oilpump switch will be enabled (block 134), after having been disabledafter oil was added for the previous batch.

In that way, the automated corn popper 10 of the present invention onlyhas to be loaded with ingredients to continually produce successivebatches of popcorn. Once the ingredients are loaded, the operator canignore the popper and the corn will be properly cooked and dumped to beready for serving. An audible buzzer 70 and flashing light 71 willconstantly remind the operator when a new ingredients load is need and acooperative working relationship between the operator and the popper isdeveloped for producing consecutive batches of fresh popcorn efficientlyand safely while leaving the operator to more important tasks such asselling the product. Furthermore, the temperature control of the popperensures that the right amount of heat is applied to each batch ofpopcorn for consistently cooked popcorn. Still further, the inventioncontrols an oil pump system to ensure that the proper amount of oil isadded without excess.

FIG. 8 schematically illustrates the kettle temperature as a function oftime through initial power-up and a single cooking cycle. When thekettle heat is turned on, the kettle 18 heats up steadily until itreaches an equilibrium start temperature as indicated by line 140.Preferably, an equilibrium start temperature will be around 500° F. to525° F., but may be adjusted accordingly, depending upon the popcornload and the size of the kettle and other heating factors as understoodby a person of ordinary skill in the art. The temperature controller 82of the invention is programmed with the equilibrium start temperatureand will automatically monitor the kettle temperature to determine whenit begins to approach the start point 144. The temperature controller 82will cycle the heater 88 accordingly to prevent a large amount ofovershoot as indicated by the decreasing slope of the curve as itapproaches line 140. When the start temperature is reached, the kettleheater 88 is cycled ON and OFF by relay 86 to maintain the kettle closeto the start temperature as indicated in the curve section designated byreference numeral 142. When ingredients, such as kernels and oil, areloaded, as indicated by the load point 144, the kettle temperature dropsoff somewhat rapidly as indicated on the curve by reference numeral 146.Depending upon the popcorn and oil load, the kettle temperature woulddrop to a low point 147, for example in FIG. 8, indicated around 325° F.As the kettle temperature drops, it will drop through a low alarm point149. This first low alarm point is designated the cycle point or cycletemperature, because the PLC 77 sees it as the beginning of a cookingcycle.

As the popcorn cooks, the kettle temperature again begins to rise asindicated by reference numeral 148 and will again pass through the lowalarm set point or dump point 150. At dump point 150, the end of thecooking cycle is indicated, and the PLC 77 responds by initiating a dumpcycle. Therefore, the cooking cycle is defined between the cycle point149 and the dump point 150, although some cooking of the popcorn willoccur before the cycle point 149 and after the dump point 150.

The dump cycle is a two-stage dump and empties the cooked popcorn ontothe serving platform to be sold. After the dumping cycle, the kettletemperature again rises to the equilibrium start temperature of 525° F.and the heater will again be cycled ON and OFF to keep the kettle atthat temperature indicated on the curve by reference numeral 152. At thestart temperature, the buzzer 70 will again sound and the light 71 willflash to indicate to the operator that a batch of popcorn has justfinished cooking and that a new load of ingredients should be added tothe kettle.

Line 154 illustrates the signal on line 94 from temperature controller82 to the PLC 77. When the low alarm temperature points are reached andexceeded (either cycle point or dump point) the output from thetemperature control cycles oscillates from high to low at an internalfrequency. The square wave signal is used preferably to drive theintermittent buzzer 70 and flashing light 71. When the temperature ofthe kettle drops below the low alarm temperature point, the output oftemperature controller 82 stays high, which indicates that a cookingcycle is ongoing.

As described, the present invention continuously and properly cookspopcorn in consecutive batches with minimal attention by the operator.Because the kettle is controlled by temperature and the dump cycle isinitiated automatically depending upon the kettle temperature, thepopcorn is not burned and is not affected by operator inattention.Furthermore, the introduction of oil is controlled for a proper,premeasured amount only once during each cooking cycle. Messes andspills associated with the prior art devices are reduced, and areduction in the delays between fresh batches of popcorn will increasethe production rate of the popper and thereby increase sales andprofitability of the popper. Furthermore, the present invention insuresthat a consistent and proper amount of heat energy is always applied tothe corn for popping. The invention is not particularly susceptible toenvironment variations, and will ensure that the proper amount of heatenergy is applied to a batch of corn. Larger batches will get more heatenergy and small batches will get less heat energy to insure consistentpopping.

Turning now to other aspects and embodiments of the invention, it willbe appreciated that the foregoing detailed specification is particularlyapplicable to automatic systems wherein the kettle is loaded and dumpedautomatically. Further alternative embodiments contemplate poppingapparatus and methods wherein the kettle may be automatically ormanually loaded and automatically or manually dumped.

For example, in one aspect of an alternative embodiment, audible and/orvisual alarms are controlled by the controller to produce an alarm whenthe kettle reaches the dumping temperature or Tdump temperature and thepopcorn is finished cooking. This alerts an operator to observe thekettle dumping or, in a manual mode, to actuate the control to manuallydump it.

An alarm is also given to alert the operator that the kettle is beingloaded when it has reached a loading temperature, or Tload temperature,or to actuate the control to load corn and oil when Tload is reached, orto load the kettle manually when Tload is reached. In one embodiment ofthe invention, the dump temperature and load temperature areapproximately the same, and an operator will dump one batch and load anew batch of ingredients at approximately the same time.

Specifically, and referring to FIG. 14, the PLC 77 or other controller,such as a microprocessor, is coupled to an audible buzzer 70 and also toone or more indicator lights 71. The controller 77 operates the audiblealarm or buzzer 70 and any particular indicator lights 71 at particulartimes to alert an operator that action is necessary with the system.

For example, controller 77, upon determining that the kettle has reacheda particular ingredient loading temperature point, will alert theoperator to load the ingredients into the kettle. Once the kettle hascooked the ingredients and completely popped the popcorn, the controllerwill again alert the operator to dump the kettle, if manual dumping isnecessary.

For each subsequent batch of popcorn, the operator will then be alertedto load ingredients for the next successive batch and will be alerted,in a manual dump situation, to dump the corn once that batch has beenpopped. Of course, in an automatic dump situation as described above,dumping will occur automatically.

Therefore, the present invention provides operator indications, eithervisibly or audibly, to alert an operator when they are supposed to takeparticular steps, such as adding ingredients and dumping popcorn.

In another aspect of the invention, the cooking process is modified toinsure that the first cycle from a cold start, or alternately, the firstand several following cycles from a cold start, are controlled to insureconsistent popcorn quality is attained in following cycles when heatequilibrium of the system has been reached.

In particular, it will be appreciated from the foregoing detaileddescription of one embodiment of the invention that the control system,and specifically temperature controller 82, analyzes the cycle and therate of heat rise of the kettle with respect to a control temperature orsome other desired temperature. As the kettle temperature increasestoward the desired temperature, the temperature controller 82 reducesthe heat energy input by reducing energy to the heating element prior toreaching the desired temperature. The temperature, however, continues toclimb in a controlled fashion toward the desired level, but ismaintained by this process closer to the desired temperature without thewide margins of overshoot as in prior systems, such as where the heatelements are fully energized up until the desired set temperature isreached. The amplitude of maximum temperature variation around thedesired temperature is significantly reduced, resulting in a closecontrol of heat energy in the process, and a consistent high quality,good tasting popcorn. The temperature controller uses a PID orproportional integral derivative scheme to operate and control thekettle heater and kettle heat.

It has been discovered that if the same control logic is applied,however, to the heat energy in the first cycle from a cold start, or inimmediately following cycles before the apparatus and sensors reachtheir own heat equilibrium, those cycles can be adversely affected tothe extent they deviate from optimum cooking cycle. This occurs, forexample, in the following manner.

If the normal temperature controller PID logic is used on start up, asthe kettle temperature rises toward the desired temperature in theinitial cycle from a cold start, the controller senses the rate of riseand retards heat input as the temperature nears the desired temperature.The desired temperature may be a load temperature or Tload for cooking afirst batch of popcorn. Since the kettle, and the sensor, and otherheated components of the system have most likely not reached thermalequilibrium (as it exists for subsequent cycles after the first cycle orthe first several cycles have run) the temperature or heat response ofthe apparatus is not the same as it is at subsequent cycles whenequilibrium has been established. The corn and oil might be loaded at aload temperature under conditions which result in a cook time outsidethe preferred range of about 3.0 to about 3.5 minutes. Specifically,when the system is not at equilibrium, heat energy added to the kettlewhen ingredients are added will not all be directed to the ingredients.Rather, system components will continue to absorb heat energy away fromthe ingredients. As such, the load temperature may be below the desiredpoint to begin the cook cycle and the ingredients will not be properlycooked when a dump temperature is reached. The FIGS. 9, 10 and 11demonstrate the effect on time to reach a set, optimum dump temperaturefor various Tload temperatures when the corn and oil are actuallyloaded.

Accordingly, this embodiment of the invention contemplates a bypass ofthe PID aspects of the invention for the first or first few cookingcycles to insure the cook time from the loading of corn and oil toreaching Tdump temperature is within the preferred range of about 3.0 toabout 3.5 minutes, and the corn is cooked properly.

FIG. 16 is a temperature graph versus time of the kettle during apopcorn cycle in accordance with one embodiment of the presentinvention. Specifically, at point 210, the system is turned on and thekettle heater begins heating the kettle such that the temperature risesaccording to slope 211. In the first cycle of the heater, where it isinitially being heated up from a cold start, the PID aspects of thetemperature controller 82 are not yet utilized in order to provide moreconsistent popping of the popcorn, even in the first cycle, or the firstfew cycles.

In earlier systems, the temperature controller 82 was incorporatedimmediately and therefore, as the kettle temperature approached aparticular desired temperature, the controller 82 would operate thekettle heaters to slow down heating of the kettle so that the desiredtemperature is approached in a more controlled manner. However, in thefirst cycle, the components of the system including the kettle 18,kettle heater 88, thermocouple and other elements have not yet reached athermal equilibrium.

As noted, it was discovered that upon introducing the temperaturecontroller 82 and its PID aspects in the first cycle, that the firstbatch of popcorn would not cook properly. Specifically, the controller82 would tend to slow the heating of the kettle down before all of thecomponents have had a chance to reach their thermal equilibrium. Thus,when the ingredients were loaded, heat directed to the kettle andcomponents, which should have been for the corn, would actually beabsorbed as the various components try to reach their thermalequilibrium.

Therefore, in accordance with one aspect of the present invention, thecontroller 77 overrides the PID features of the temperature controller82 for the first cycle and simply turns on the heaters and lets thekettle temperature ramp up toward a Tcontrol temperature which isessentially a high limit temperature. At some temperature prior toreaching Tcontrol, the kettle heater 88 is turned off, such as at point212.

Due to the time and temperature lag within the system, which iscumulative for all the components in the system, the kettle will stillcontinue to be heated, as indicated by the portion of the slopedesignated with reference numeral 213. In fact, the kettle temperaturewill pass up through a dump temperature or load temperature point 214and will continue to approach Tcontrol. The controller 77, based uponthe power of the heating elements and the overall mass of the kettle andcomponents, will be programmed to turn the kettle heat off, such as atpoint 212, in order to insure that the overall temperature of the kettledoes not reach and exceed Tcontrol.

Tcontrol, as discussed further hereinbelow, is a maximum limittemperature. If the kettle temperature reaches and exceeds Tcontrol, thekettle heat will turn off and remain off until the system can beadjusted or fixed. However, in the first cycle, the Tcontrol temperatureis utilized as an upper limit and the controller 77 turns the kettleheaters off substantially below that point so that any temperature lagwithin the system will not bring the kettle temperature beyond Tcontrol.However, since no PID control is utilized, heat is directed to thekettle rapidly without a typical PID slowdown. In that way, the systemgets closer to an equilibrium state on the first cycle.

As the kettle temperature passes through the Tload point 214, theoperator is alerted to add ingredients, since the kettle is at thedesirable cooking temperature.

If no ingredients are added, the kettle temperature will climb to itshighest point as indicated by a peak point 215 and will then start tocool because the heater has been turned off. However, during normaloperation, the operator will load the ingredients, such as popcorn andoil, which present a thermal load to the kettle as discussedhereinabove. The kettle heat then begins to plummet according to theportion of the curve indicated by numeral 216.

As the corn pops, the various ingredients absorb heat so that the kettletemperature continues to decrease down to a certain lowpoint 217.Controller 77 continues to monitor the kettle temperature and thecontroller knows that a cooking cycle has begun when the kettletemperature dips below some chosen temperature point, such as around 370degrees.

Continuing in the cooking cycle, once the ingredients have absorbedsufficient heat to cook the popcorn, the kettle again begins to heat upfrom point 217 as the heaters continue to apply heat to the kettle. Itshould be noted that when the kettle temperature passes through theTdump point or Tload 218, as it cools down after ingredients have beenloaded, the PID features of the temperature controller 82 take over andthe system is then under control of those PID features until the systemis turned off and again begin with the next cold start cycle.

The PID features of the temperature controller 82 will kick in when thekettle temperature cools down, regardless of whether ingredients havebeen added. For example, even if no ingredients are added, the heater isturned off in the initial heat cycle at point 212 and therefore thekettle temperature will inherently cool down from its peak point 215 toTdump at point 218. At that point, the PID features of the temperaturecontroller 82 take over and the kettle heater will again be turned on todeliver heat to a batch of ingredients or to keep an empty kettle aroundthe desired Tload/Tdump point.

As the heater continues to add heat to the kettle, the kettletemperature will begin rising, as designated by the portion of the graphindicated with reference numeral 219. However, the control of theheater, and therefore the kettle temperature, at that point is withinthe PID aspects of controller 82. Therefore, the temperature will rampup more gradually to a Tdump point in those cycles subsequent to thefirst cycle.

Once the kettle heats up to the Tdump point 220, several things mightoccur. In a system which utilizes a manual dump, the controller 77 willaudibly and/or visibly alert an operator, such as through an audiblebuzzer 70 or indicator light 71, that the load needs to be dumped. Thisis particularly important as an operator may be busy and distracted andthe popcorn must be dumped before it burns. Burnt popcorn is asignificant problem in certain vending situations. Alternatively, if thesystem is operable to automatically dump the kettle, the kettle may beautomatically dumped at temperature point 220. Controller 82 thenoperates the kettle heater, such that the kettle heat is maintainedaround the Tload/Tdump temperature as indicated by reference numeral222. As the system reaches equilibrium, the overshoots associated withregion 222 will decrease for subsequent cycles.

At that point, the next batch of ingredients should be loaded.Therefore, the Tdump is also indicated as Tload. Once the next batch ofingredients is loaded, such as at point 224, the temperature of thekettle will again drop as it repeats another cooking cycle as previouslydescribed. For each subsequent cycle, the kettle and kettle heater areunder the control of the PID aspects of the temperature controller.

While one embodiment of the invention is described with respect tobypassing the PID aspects of the temperature controller for the firstcycle, so that the system may reach equilibrium and the first batch ofpopcorn is cooked properly, such a feature may be incorporated with morethan the first cycles, such as the first two or three cycles, in orderto insure that equilibrium is properly obtained before turning thekettle heater over to the control of the PID aspects of the temperaturecontroller. Therefore, the invention is not limited to simply a singleoverride of normal kettle temperature control within the first cycle.

As discussed above, should the kettle temperature meet or exceed the setTcontrol temperature, the controller 77 recognizes an over temperaturecondition and will shut off the heater to the kettle.

FIG. 15 discloses a flow chart for operation of one embodiment of thekettle where, more specifically, the kettle is heated according to step226. The controller 77 determines if the kettle is starting from a coldstart (step 228). If it is, the kettle is heated without PID control toa set point and the heater is then turned off (step 230). Then,controller 77 determines if the kettle temperature is cooled to Tload.If it has, whether that is through the kettle simply cooling downbecause heat to the kettle was turned off, or the loading ofingredients, the controller 77 initiates the PID aspects of thetemperature controller 82 for subsequent cooking cycles (steps 232 and234). If the kettle is not starting from a cold start as it is beingheated, the PID control aspects are utilized (step 234).

Again, while the example is given for a single start up cycle, numerouscycles might be utilized from a cold start before equilibrium isreached, and therefore control of the kettle heating may not be turnedover to the PID aspects of temperature controller 82 until after severalcycles.

In another aspect of the invention, the foregoing detailed descriptiondescribes the delivery of oil by means of a pump and timer. It has beenfound that calibration of the timer is an awkward, trial and errorprocess, not enjoyed by most operators. Accordingly, this inventionfurther contemplates the use of the controller 77 to control delivery ofconsistently measured amounts of oil. The controller is operable to beplaced in a learn mode upon the initial cooking situations. The pump isstarted and oil is dispensed into a desired measurement receptacle. Whenthe exact amount is dispensed, the pump is stopped. The control system“learns” this sequence to so that any further initiation of the oildispensing cycle causes the same amount of oil to be dispensed.Therefore, the aforementioned timer and trial and error process iswholly eliminated with the control provided by controller 77.

For example, when initially beginning the cooking of popcorn, the oilsystem is placed in a measurement mode in order to set how much oil willbe automatically added each time in the cooking cycle or will be addedmanually upon engagement of an oil pump button or switch at the start ofa cook cycle.

The timer associated with the oil pump is bypassed with the controller77 controlling the pump timing in order to deliver the proper amount ofoil for each batch of popcorn. To that end, oil pump control circuitry200 is operably coupled to the controller 77 to place the controller 77in a “learn” mode (see FIG. 14).

Upon initiating the oil pump control circuitry 200 to place thecontroller 77 in a learn mode, and upon engaging the pump switch 106,the oil pump begins pumping oil and the controller 77 monitors how longthe oil pump switch is engaged. The oil pump control 200 places thecontroller 77 into a learn mode so that it monitors the length of timethat the switch 106 is engaged. Once the switch 106 is disengaged, thecontroller 77 remembers the particular length of time. In that way, aparticular length of time may be associated with a particular amount ofoil being dispatched. The oil pump control circuitry 200 may beimplemented with the existing circuitry, such as by manipulating, insequence, switch 106 and other switches associated with the oil pump andcoupled to controller 77.

As an example, the oil pump may be capable of dispensing one half of acup of an oil in 2 to 3 seconds. If the oil pump control 200 is engagedand the controller 77 is set up to learn, the controller 77 willremember the time of 2 to 3 seconds that the switch is initially engagedand will dispense the amount of oil associated with that time, that is,approximately one half of a cup of oil. The controller may then be takenout of learn mode by control 200. Thereafter, each time switch 106 isengaged, approximately one-half cup of oil is dispensed.

To determine the proper amount of oil, an operator may hold a measuringimplement, such as a measuring cup, under the oil inlet leading to thekettle. The switch 106 is then engaged for a particular amount of timein order to deliver a desired amount of oil to the measuring cup. Oncethat desired amount of oil has been delivered, the controller willremember.

For each subsequent batch of popcorn, the controller will operate theoil pump 104 to dispense oil for a particular amount of time. In thatway, the trial and error associated with setting a specific oil pumptimer to deliver the proper amount of oil, is eliminated. Rather, theoperator may watch the amount of oil which is initially delivered andwill disengage the switch 106 when the proper amount is delivered.Assuming that the oil pump is consistent in its pumping rate, thecontroller 77 will then remember the time and operate the pump for theproper time to insure the proper amount of oil. The operator does notcare about the specific time, but rather wants to insure that a specificamount of oil is added each time, regardless of how long the oil pumphas to operate to do so. Therefore, the present invention insures that aproper amount of oil is added each time and eliminates the need for theoperator to adjust oil pump timers and the trial and error process tomeasure the oil added to the kettle.

In another aspect of the invention, it is noted that popcorn machinesmay be used not only to pop corn with a salt seasoning, but also to popcorn in sugar, producing a coated, sweet caramel-like tasting popcornproduct. This product is perhaps more popular in European environmentsthan in U.S. Use of a popper according to any embodiment described abovecan produce such product, but if the same temperatures are used, thesugar can be heated too much and burned. Accordingly, one embodiment ofthe invention contemplates the use of control circuitry enabling thecooking temperatures to be adjusted to the popcorn product desired.While this may be at the expense of optimum popped corn when lowertemperatures are selected for “sugar” corn, other operating processes asdescribed herein are retained.

Specifically, salt popcorn may be popped at a temperature of, forexample, 525 degrees F. However, popping sugar popcorn at such atemperature would burn the sugar. Therefore, one embodiment of thepresent invention utilizes a cooking temperature control circuit 202which is coupled to controller 77 for varying the cooking temperature ofthe kettle through the temperature controller 82.

Specifically, the cooking temperature control circuit 202 may include anumber of switches or other circuits, such as circuit jumpers, such thatit is slightly higher for salt popcorn and slightly lower for sugarpopcorn. The cooking temperature control circuit 202 may be set duringmanufacturing, such as by utilizing specific jumpers associated withcontroller 77 to select a temperature for Tload/Tdump. Each jumper mayrepresent a certain temperature range for reducing a salt corntemperature of Tload to a sugar corn Tload. More precise temperatureadjustments might be provided by using potentiometers with the jumper tovary the selected temperature with controller 77.

Alternatively, the cooking temperature control circuit 202 might beaccessible to the operator, such that the operator may select the typeof popcorn to be cooked. For example, a simple two-position switch mightbe used, with one for salt and one position for sugar.

Generally, popcorn poppers will be set up for cooking one type ofpopcorn and will not be switched back and forth between types ofpopcorn. For a single use situation, hard wiring of a cookingtemperature control circuit 202 at the manufacturing level may bedesirable. However, if a particular machine will be switched back andforth and do double duty with both salt popcorn and sugar popcorn,operator-accessible control circuitry might be utilized.

In yet another aspect of the invention, it is desirable to provide avisual indicator in a popper that the kettle is not ready for cornloading, such as before the kettle temperature has reached Tload.Accordingly, on startup, the controller in an automatic dump machinetilts the kettle, such as to a 45 degree angle, for example, to indicateit is in a non-loading portion of the cycle. The kettle is leveled whenits temperature reaches a desired Tload to visually indicate it is readyfor loading. The control system accomplishes this similar to the way inwhich the kettle is controlled for an automatic dump as will beunderstood by a person of ordinary skill in the art from the foregoingdescription.

Finally, it will be appreciated one embodiment of the inventioncontemplates a manual operation of the kettle position through dump andreturn, and which is particularly enhanced by the provisions of the loadand dump alarms described above.

The present invention also provides the proper amount of heat tomaximize kernel expansion at popping. With the heat maintained at theproper level, the temperature of the corn and the steam pressure in thekernels will cooperate to provide consistent and high kernel expansion.With the present invention, popping expansion of rates of 1:50 have beenachieved which are a significant improvement over the 1:44 or lowerrates achieved by the prior art.

While the present invention has been illustrated by a description ofvarious embodiments and while these embodiments have been described inconsiderable detail, it is not the intention of the applicants torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. The invention in its broader aspects istherefore not limited to the specific details, representative apparatusand method, and illustrative example shown and described. Accordingly,applicant intends to be bound only by the claims appended hereto.

What is claimed is:
 1. A method of cooking a first batch of unpopped corn in a heated kettle wherein kettle heating elements are controlled by an electronic control receiving a temperature responsive signal from a heat sensor on said kettle, said method comprising: energizing said elements when said kettle is cold, maintaining delivery of energy to said kettle until said sensor signals said control that a first temperature has been reached, and then reducing said energy, generating a signal when said kettle reaches a second higher loading temperature, and thereafter loading the first batch of unpopped corn and oil into said kettle and cooking the unpopped corn so as to pop the corn to produce cooked popcorn.
 2. The method of claim 1 including the step of dumping said cooked popcorn from said kettle when, after the loading of corn and oil, said kettle reaches a dump temperature substantially the same as said second temperature.
 3. The method as in claim 2 including cooking a second batch of unpopped corn by the subsequent cooking steps of sensing a third temperature lower than said first temperature and reducing the delivery of energy to said elements upon said sensing of said third temperature and thereafter loading the second batch of unpopped corn and oil into said kettle when said second higher temperature is reached and cooking the unpopped corn so as to pop the corn to produce cooked popcorn.
 4. The method as in claim 1 including generating a first signal observable by an operator upon said kettle's reaching said second temperature to indicate the kettle is ready for loading of said first batch of unpopped corn and oil, and generating a second signal upon said kettle's reaching a predetermined temperature indicating popping of said first batch of unpopped corn is complete and the kettle can be dumped.
 5. The method as in claim 1 wherein said unpopped corn is popped in a period of about 3.0 to 3.5 minutes from the time corn and oil is loaded into the kettle to the time a predetermined dump temperature is reached and the corn is popped.
 6. The method as in claim 1 wherein temperature of said kettle declines when corn and oil is loaded therein and wherein said method includes: electronic controlling of said heating elements to cause said kettle to reach a dump temperature substantially equal to said second temperature within a time of about 3.0 to 3.5 minutes from loading of corn and oil wherein popped corn can then be dumped from said kettle. 